Heat treatment of a platinum-gallium alloy for jewelry

Abstract

A platinum alloy containing 1 to 9 percent gallium and minor amounts of property enhancing additives, eg. up to 3% Pd. This alloy can be heat-treated to a Vickers hardness that is increased by at least over 25% beyond its initial, untreated value and typically to at least over 300 HV. The heat-treatment process includes the steps of solution-treating the alloy, followed by quenching and a hardening heat-treatment to achieve the desired hardness and strength. The alloy is useful as a component of jewelry, art objects or related articles.

What is claimed is: 
     
       1. A method for making jewelry, which comprises: formulating a platinum alloy which consists essentially of at least about 95 weight percent platinum, about 1 to 5 weight percent gallium, and an additional alloying element of palladium in an amount effective as a property enhancing agent but less than about 3 weight percent, said alloy having an initial Vickers hardness;   heat-treating the alloy to increase the Vickers hardness by at least about 25% but to not greater than a Vickers hardness of 385; and   utilizing the heat-treated alloy as a component of jewelry.   
     
     
       2. The method of claim 1 wherein the property enhancing agent is a deoxidizing agent, a grain reducing agent, a viscosity decreasing agent or a color variation agent; and the heat-treating operation comprises solution-treating the alloy at a temperature of at least about 1700° F; quenching the solution-treated alloy to a temperature of below about 200° F; and hardening the quenched alloy at at least 900 F for a sufficient time to achieve the desired hardness. 
     
     
       3. The method of claim 2 wherein the solution-treating temperature is a least 1800° F, the alloy is held at that temperature for at least 10 minutes, the solution-treating step is an annealing step conducted in an inert, non- or anti-oxidizing environment, and the annealed alloy is quenched in water. 
     
     
       4. The method of claim 2 wherein the hardening heat-treatment is conducted by heating the alloy in an inert, non- or anti-oxidizing gas atmosphere for at least 30 minutes at about 1100° to 1200° F. 
     
     
       5. The method of claim 4 wherein the hardened alloy is cooled to room temperature. 
     
     
       6. The method of claim 1 which further comprises forming the alloy into a desired shape of the jewelry component prior to the heat-treating operation. 
     
     
       7. The method of claim 6 wherein the forming operation includes casting, forging, drawing, stamping or rolling the alloy. 
     
     
       8. The method of claim 1 which further comprises treating the hardened alloy to remove or prevent surface oxidation. 
     
     
       9. The method of claim 8 wherein the alloy is shielded to prevent surface oxidation. 
     
     
       10. The method of claim 6 wherein the alloy is formed into a sheet, wire, or cast object. 
     
     
       11. The method of claim 2 wherein the annealed object is formed into a shape useful as a jewelry component before the quenching step.